22.8 Performance Schema General Table Characteristics

The name of the performance_schema database is
lowercase, as are the names of tables within it. Queries should
specify the names in lowercase.

Most tables in the performance_schema database
are read only and cannot be modified. Some of the setup tables
have columns that can be modified to affect Performance Schema
operation; some also permit rows to be inserted or deleted.
Truncation is permitted to clear collected events, so
TRUNCATE TABLE can be used on
tables containing those kinds of information, such as tables named
with a prefix of events_waits_.